Only when it became clear that the vice president wanted to express himself did his entourage stop interrupting to let the candidate speak.

When he did, Biden recalled his own family tragedy — losing his young wife and daughter in a 1972 car accident — and paused repeatedly to keep his composure.

It was the side of Biden — comfortable with his emotions, and with a gift for human connection — that makes him appealing to many voters. And the moment never would’ve taken place if he had not effectively overruled his would-be handlers.

It was a vivid illustration of a phenomenon that pervades the 2012 campaign: The consuming effort by operatives to stamp the spontaneity and life out of modern politics.

Of course, Biden’s two-day swing through small-town Virginia also offered a perfect example of why this brand of control-freak politics has emerged. His unrehearsed comment to a mixed-race audience in Danville that the Republicans and their Wall Street allies want to put people “ back in chains” made national news as an example of rhetorical excess.

In an era of Twitter and saturation news coverage — when one stray remark can upend a day’s news cycle and campaigns struggle to shape their preferred message — politicians and their aides are increasingly intent on restricting the media’s interaction with candidates. Barack Obama or Mitt Romney both shun the sort of freewheeling news conferences that used to be a staple of campaigns. And when reporters do seek to engage the candidates, the staff minders attempt to shut it down with ham-handed aggressiveness.

All candidates live with the contradiction — a media culture that implores politicians to seem authentic but is ready to punish them when they really are — but the challenge is especially exquisite in Biden’s case.

He is an irrepressible, garrulous and emotive politician, who’s flourished and fumbled through 40 years in national office by practicing politics the old-fashioned way — from the gut and without much script. He’s as fine a one-on-one politician of any officeholder of his generation, a talent especially prized because it is not a particular gift of Obama’s.

But his penchant for off-message moments regularly sends aides in the West Wing and at Chicago reelection headquarters into orbit.